A conventional scissor jack shown in FIG. 4 includes a handle 11 with the help of a pipe member 12 for pressing oil from an oil storing cylinder 13 into an oil pressure cylinder 15 mounted on a base 14 so that a piston rod may lifted up and then connecting rods 16, 16 are raised up to push lift arm units 17, 17 for raising up an object.
The conventional scissor jack has drawbacks as follows:
1. As rollers are not: provided under the base for moving around the scissor jack, the jack is not easy for moving on the ground. PA1 2. The lift arm units may not be stabilized in moving down because of too heavy weight of an object to be lowered or unstable flowing speed of oil back in a reservoir. PA1 3. The reservoir is separately combined with the base, not convenient for assemblage.